The thing I've seen is attached either to the driver's side or the 
passenger's side window, and is a metal cylinder.  One fills it
with either water or water and ice, and it cools by evaporation
in non-humid climates, and can, I'm told, reduce interior temperatures
by about 20 degrees F.  They were made by companies like Firestone
here in the us in the 40s or so, and are now speciality items
seen at swap meets, etc, and VERY expensive.  I've been quoted
prices as high as $350, which I of course refused to pay.  I
AM curious about these water bags, or soaked canvas things.  Does
someone care to make an ascii?

/martha